Cell Communciation

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  • NO – local regulator – help with relaxation of smooth muscles – viagra – allows for erection of penis – if released by endothelial cells Can act as a neurotransmitter if released by neurons; kills backter and cancer cells if secreted by WBC
  • Cell Communciation

    1. 1. Cell Communication
    2. 2. Cell “signaling” <ul><li>Direct communication between cells </li></ul><ul><ul><li>Cell junctions between adjacent cells </li></ul></ul><ul><ul><li>Cell-cell recognition through interaction of surface protein </li></ul></ul><ul><li>Communication via signals between cells (signal transduction pathways) </li></ul><ul><ul><li>Local signaling </li></ul></ul><ul><ul><li>Long distance signaling </li></ul></ul>
    3. 3. Direct Communication <ul><li>Gap junctions & Plasmodesmata </li></ul><ul><ul><li>Results in cytoplasmic continuity favoring cellular interactions </li></ul></ul>
    4. 4. Direct Communication <ul><li>  Cell surface contacts </li></ul><ul><ul><li>Receptor protein specificity </li></ul></ul>
    5. 5. Direct Communication: Surface Proteins - Yeast Cells <ul><li>Mating in yeast cells </li></ul><ul><li>a cell </li></ul><ul><ul><li>Releases a-factor that binds to  cell receptors </li></ul></ul><ul><li> cell </li></ul><ul><ul><li>Releases  -factor that binds to a cell receptors </li></ul></ul><ul><li>Results </li></ul><ul><ul><li>Fusion of 2 cells (mating) producing diploid cell </li></ul></ul>
    6. 6. Direct Communication: Surface Proteins - Yeast Cells
    7. 7. Signal Transduction Pathways <ul><li>Local communication </li></ul><ul><ul><li>“Transmitting cell” secretes a local regulator (molecule that “talks” only to cells close by) </li></ul></ul><ul><li>Long Distance communication </li></ul><ul><ul><li>“Transmitting cell” secretes a molecule that travels long distances to reach its target cell </li></ul></ul>
    8. 8. Local Communication <ul><li>Paracrine Signaling </li></ul><ul><ul><li>Cell secretes a molecule that interacts with a target cell nearby </li></ul></ul><ul><li>Synaptic Signaling </li></ul><ul><ul><li>Cell releases a neurotransmitter into a synapse between two cells that are nearly touching </li></ul></ul>
    9. 9. Long Distance Communication <ul><li>Endocrine signaling </li></ul><ul><ul><li>Specialized cells release molecules (hormones) via blood stream </li></ul></ul><ul><ul><li>Hormones move to distant target cells to elicit response </li></ul></ul>
    10. 11. Signal Transduction Pathway
    11. 12. 3 Steps in Signal Transduction <ul><li>Reception of the signal </li></ul><ul><li>Transduction of the message to the intended “receiver” </li></ul><ul><li>Response to the message </li></ul>
    12. 13. Signal Reception <ul><li>Lock-&-key analogy (enzyme-substrate recognition) </li></ul><ul><li>Ligand molecules (Signal molecule) interacts with receptor protein </li></ul><ul><ul><li>Receptor protein bound in the plasma membrane </li></ul></ul><ul><li>Conformational change of ligand-receptor causes activation </li></ul>
    13. 14. Examples of membrane associated receptor molecules <ul><li>G-Protein linked receptors </li></ul><ul><li>Tyrosine-kinase receptors </li></ul><ul><li>Ion-channel receptors </li></ul><ul><li>Exception </li></ul><ul><ul><li>Intracellular receptors </li></ul></ul>
    14. 15. G-Protein linked Receptors <ul><li>Functions </li></ul><ul><ul><li>Embryonic development </li></ul></ul><ul><ul><li>Vision and smell sensory reception </li></ul></ul><ul><ul><li>Bacterial infections </li></ul></ul>
    15. 16. <ul><li>G-protein acts as the ON-OFF switch </li></ul><ul><li>Inactive form when bound to GDP </li></ul><ul><li>Active form when bound to GTP </li></ul>
    16. 17. Tyrosine-kinase Receptors <ul><li>Function </li></ul><ul><ul><li>Receives “growth factor” signals that stimulate cell division </li></ul></ul><ul><ul><li>Uncontrolled cell growth - cancer </li></ul></ul>
    17. 18. <ul><li>Inactive form – Exists as single polypeptides </li></ul><ul><li>Active form – Formation of a dimer that acts as an enzyme and its own substrate </li></ul>
    18. 19. Ion-channel Receptors <ul><li>Important in the nervous system </li></ul>
    19. 20. Exception <ul><li>Intracellular Receptors </li></ul><ul><ul><li>Signals able to pass through the plasma membrane </li></ul></ul><ul><ul><li>Small molecule (NO) or lipid soluble (testosterone) </li></ul></ul><ul><ul><ul><li>Nitric oxide </li></ul></ul></ul><ul><ul><ul><ul><li>Relax smooth muscle </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Act as a neurotransmitter </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Help kill unwanted cells </li></ul></ul></ul></ul>
    20. 22. Signal Transduction <ul><li>Enzyme Cascade </li></ul><ul><li>Second Messengers </li></ul><ul><li>Amplification </li></ul><ul><ul><li>Multi-step pathway to turn “on” many different target molecules </li></ul></ul><ul><ul><li>More steps involved = more activated products </li></ul></ul>
    21. 23. Signal Transduction <ul><li>Domino Effect </li></ul><ul><li>Enzyme Cascade </li></ul><ul><ul><li>Protein phosphorylation </li></ul></ul><ul><ul><ul><li>Protein kinase </li></ul></ul></ul><ul><ul><ul><ul><li>Adds phosphates to substrate from ATP </li></ul></ul></ul></ul><ul><ul><ul><li>Protein phosphatase </li></ul></ul></ul><ul><ul><ul><ul><li>Removes phosphates from substrate </li></ul></ul></ul></ul>
    22. 24. Enzyme Cascade
    23. 25. <ul><li>Gene Activation </li></ul>
    24. 26. Second Messengers <ul><li>“ Activated relay molecule” </li></ul><ul><li>Participate in G-protein linked receptors & tyrosine-kinase receptor </li></ul><ul><li>Types </li></ul><ul><ul><li>cyclic AMP </li></ul></ul><ul><ul><li>Calcium ions </li></ul></ul><ul><ul><li>DAG (Diacylglycerol) </li></ul></ul><ul><ul><li>IP3 (Inositol triphosphate) </li></ul></ul>
    25. 27. G-protein & cAMP <ul><li>Epinephrine & glycogen breakdown </li></ul>
    26. 28. Calcium ions <ul><li>Muscle Contraction </li></ul><ul><li>Neurotransmitter release </li></ul>
    27. 30. Cellular Response <ul><li>Cellular activity/metabolism </li></ul><ul><li>Rearrangement of cytoskeleton (movement) </li></ul><ul><li>Specific gene activity </li></ul><ul><li>Synthesis of enzymes or regulate the activity of an enzyme </li></ul>

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